Essentially
Middle-Side (M-S) stereo is created using two microphones. A
Mid microphone which is usually a cardioid mic is set to face
the centre of the sound source and the Side microphone which
is always a figure 8 pattern is set up at right angles to the
Mid mic, as close as possible. This arrangement means that the
null in the figure 8 pattern faces the sound source and the
mic picks up information equally from the left and right side
of the room. In itself if you play back these two mic tracks
you get no sense of stereo at all and the secret is that to
create a complete stereo image from Mid-Side signals, you have
to ”decode" them with a special sum-and-difference
matrix.
There are a number of Mid-Side decoders available as stand alone
units or built into certain mic preamps but by far the easiest
way to decode the signal is by using the a software decoder
in a DAW like Cubase. When you have recorded the two tracks,
simply duplicate the side Figure 8 mic track. Then pan these
two tracks, one left and one right and put one of the pair out
of phase with the phase button at the top of the track on the
mixer page. Next link these two tracks together
and as you add this pair to the centre mic which is panned dead
centre and you get a very engaging and realistic stereo picture.
Click on the video link at the top of the page to see a short
video on how it's done.
Cubase also has a built in M-S decoder in the ToolsOne plug
in but
even if you aren't running Cubase you can get a great free M-S
decoder, the Voxengo
MSED. The Voxengo site has some great software
plugins and the MSED is really good and it's free!
How much of the side pair you add is down to you and the beauty
of M-S is that you can alter the stereo spread in post production.
Adding more side information makes the stereo wider but you
can also make the source seem closer by increasing the level
of the mid microphone signal and you can even manipulate the
stereo picture using the pan pots on the two side tracks. Obviously
as you pan in the side channels the stereo image gets
narrower and the mid-mic signal gets louder. Panning the left
and right side-mic channels to dead centre (that is, to mono)
effectively removes the side-mic signals and increases the mid-mic
signal by 6 dB. Quite often when recording a singer I will use
a M-S set to capture some of the room ambience and I always
think that stereo miking captures a quality that a mono mic
never quite achieves. Of course if it's not the effect you want
in the mix then you can simply loose the side info. But give
it a go on vocals and acoustic instruments. Multi pattern condenser
mics with a figure 8 switch are made by most companies but don't
forget that all ribbon mics by their nature have a figure 8
pick up pattern and the new Golden
Age R1 ribbons are a great budget mic for
getting into Mid/Side and Blumlein pair recording.
However, even if you don’t have a decent figure 8 mic
you can achieve the same effect using a pair of cardioids, one
pointing left the other right as close to the centre mic as
possible. I like Mid-Side stereo a lot and particularly with
the mobile if the room is not great you can really play with
the stereo image back in the studio. Just for a final note :try
replacing the mid cardioid mic with an omni for a more spacious
sound.
